1. Field of Invention
The present invention concerns an apparatus for the continuous manufacture of an endless strip of thin chipboard.
2. Description of Related Art
An apparatus for the continuous manufacture of an endless strip of thin chipboard is disclosed in document DE-PS No. 20 34 853 in which a conveyor belt running beneath a means for depositing wood chips consists of a steel belt wound around a heated compression roller. On account of the high specific heat of the steel belt, the heat absorbed by the belt, as it winds around the heated compression roller, is transmitted to the deflector rollers over which the belt is run and is dissipated in the surrounding air by radiant and cooling effects. This process results in some undesirable heat losses. The heat dissipation also is, however, a necessary part of the process and has to be reinforced by cooling in the vicinity of the depositing means. There, the temperature of the steel belt must not be allowed to exceed the level at which the bonding agent would not act to bond the chips which are treated with the bonding agent. As the relatively long steel belt cools off, irregular cooling of the edge zones compared with the central area occurs and may induce stresses in the steel, premature fractures or, at the very least, cracking. Because the return of the steel belt to the depositing means requires use of a lengthy steel belt which has a high unit cost per foot of belt, a substantial level of investment is needed in this regard.
An apparatus of this type is also described in document DE-OS No. 27 10 000 in which the conveyor belt running beneath the depositing means consists of two steel belts. A first belt is wound around a compression roller. A second steel belt is an endless belt separate from the first steel belt and does not have to resist such high traction forces as the first steel belt does. The second belt can thus be made of lower grade steel at lower cost. A further way of realizing possible savings in this area is that since at least two deflector rollers are used with this steel belt, smaller diameter rollers can be used. The diameter of these rollers is, however, large enough to leave a long gap between the last deflector roller and the counter-roller, as seen in operation. As a result, a lengthy guide piece is provided with which the particle mat, after dispersion and pressing, can be guided over the section between an upper tangential plane of the last deflector roller and the counter-roller. However, the particle mat exerts such a high level of friction on this long guide piece that deformation occurs in the pressed particle mat. The friction tends to alter the internal structure of the individual chips and to destroy the bonds between the chips resulting from the prepressing process. This results in a finished chipboard with poor mechanical qualities.
The purpose of the present invention is thus to provide an apparatus that avoids the disadvantages of the above second disclosure and can be manufactured at even lower cost. Its operation involves the creation of less heat while at the same time maintains the quality of the finished chipboard.
The teaching embodied in this invention provides a solution to match these requirements.